Power-supply device for working machine such as a spark-erosion machine

Abstract

A power-supply device for a working machine such as a spark-erosion machine, arc welding machine or the like substantially eliminates the break-down or misoperation of thyristers used in the device and wherein the device includes a circuit which comprises a power transformer, a thyrister rectifying circuit, a diode rectifying circuit, and a trigger circuit for triggering the thyrister of the thyrister rectifying circuit.

What is claimed is: 
     
       1. Power-supply device for a working machine such as a spark-erosion machine, arc welding machine or the like comprising: (1) a power transformer having a main secondary circuit and an auxiliary secondary circuit, said main secondary circuit and said auxiliary secondary circuit being respectively provided with additional normal and inverse turns in addition to the desired number of normal turns which generates desired output current,   (2) a thyrister rectifying circuit having a first thyrister, said thyrister rectifying circuit being connected to said main secondary circuit,   (3) a diode rectifying circuit connected to said auxiliary secondary circuit parallel to said thyrister rectifying circuit, and   (4) a first trigger circuit for triggering said first thyrister of said thyrister rectifying circuit.   
     
     
       2. Power-supply device according to claim 1, wherein the short-circuit current of said auxiliary secondary circuit is predetermined to be smaller than that of said main secondary circuit and the no-load voltage of said auxiliary secondary circuit is predetermined to be equal or higher than that of said main secondary circuit. 
     
     
       3. Power-supply device according to claim 1, further comprising a second trigger circuit which comprises a second thyrister, said first thyristor being triggered by said second trigger circuit, said second thyrister being triggered by a blocking oscillator by way of a pulse transformer. 
     
     
       4. Power-supply device according to claim 1, wherein a protecting condenser is provided between the cathode and gate of said first thyrister. 
     
     
       5. Power supply device according to claim 3, wherein said pulse transformer comprises coil means forming a primary pulse transformer circuit, said blocking oscillator comprising the last said coil means, said blocking oscillator further comprising a transistor and a feedback resistor operatively connected to one another.